The Journal of Laryngology and Otology August 1979. Vol. 93. pp. 759-767
Recent research and its relevance to clinical otology* By HAROLD F. SCHUKNECHT,
M.D.f
IT is an exceptional pleasure to be once again with my British friends and colleagues, and I feel honored to have been chosen to present this address. The man whom we are honoring tonight, James Yearsley (Fig. 1), was one of the pioneers of British otolaryngology, and I am pleased that my name can be linked with his in this small way. Yearsley was born in 1805, studied at St. Bartholomew's Hospital and received his medical degree at St. Andrew's. In 1838 he founded the Metropolitan Ear Institution which later became and remains your well-known Metropolitan Ear, Nose and Throat Hospital. He was one of the founders of the Medical Directory which preceded your Medical Registry. Probably his most significant contribution to otology was his demonstration that prostheses, such as pledgets of moist cotton-wool, could be used to enhance sound transmission in defective middle ears. He carried on a large practice in London and died in 1869 at the age of 64 (Scott Stevenson and Guthrie, 1949). Your committee suggested the title 'Recent Research And Its Relevance To Clinical Otology'. It was with some reluctance that I accepted a subject of such broad scope. In dealing with such a subject there is a strong inclination to give an account of facts which are probably well-known to everyone and to make a large number of predictions with the expectation that a few of them will come true. I have made a concerted effort to avoid this approach, with, I fear, only partial success. I may also have transgressed the rule that a speaker should limit his remarks to subjects about which he has some knowledge, but you can be the judge of that. Sensorineural Hearing Loss Recently there has been a great deal of noisy enthusiasm for the cochlear implant; but what is the real potential of this device for the rehabilitation of profoundly deaf individuals? Single electrode implants are a reality, of course, and the ingenuity and courage of surgeons who have implanted them deserves our admiration. However, the implant is receiving too much attention at this time. In the first place, the total pool of candidates suitable for implantation is quite small. Secondly, the technology is * Twenty-Fifth James Yearsley lecture presented at the Royal College of Medicine on March 2, 1979. f Chief, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Professor of Otology and Laryngology, Harvard Medical School. 759
760
H. F. SCHUKNECHT
FIG.
1
FIG.
2
RECENT RESEARCH AND ITS RELEVANCE TO CLINICAL OTOLOGY
761
too primitive to justify widespread use at this time. Probably the most serious obstacles in the path of success of implantation are the paucity of cochlear nerve fibres in most ears with profound deafness, and the additional damage which is almost certain to result from implantation (Otte et ah, 1978). None the less, the drama will proceed and some good may eventually come of it. A much greater health problem facing us is the great multitude of disabled people with subtotal sensorineural hearing loss. With the virtual elimination of acute bacterial infection as a cause for hearing loss, the most common type now encountered is presbycusis. Several pathological types of presbycusis have now been described and the success of amplification depends entirely on the type. For example, in the strial atrophy type in which hair cells and neurons are functional, stimulus coding and consequently speech discrimination are excellent and amplification is highly successful. In the neural atrophy type, on the other hand, in spite of functional stria and hair cells, the discrimination is poor and amplification is less helpful (Schuknecht, 1974). Presbycusis is caused by degenerative changes occurring in 'fixed postmitotic' cells. These specialized cells have no regenerative powers and once damaged cannot be replaced. Presbycusis should be viewed as the auditory manifestation of a diffuse process which involves all the body tissues. Within the fourth decade of life there already is decreased efficiency in some organs and of the individual as a whole. In the fifth decade there is a more apparent reduction in efficiency, and the further passage of time brings a cascading of senile events which terminate in death in the seventh or eighth decade of life. The manner in which we age is largely determined by genetic factors. Unless an unexpected breakthrough occurs in the research on aging there will be no prevention of presbycusis and it will become increasingly prevalent as survival time increases. The effect on hearing of a lifetime of noise exposure is not known. How harmful are household noises and street noises? This question has not been answered. Certainly the noises of industry, motor vehicles, firearms and amplified music are responsible for many handicapping losses. Many animal studies have been performed in which various acoustic stimuli have been correlated with morphological changes in the cochlea. These studies have aided in establishing damage risk criteria. There is now general awareness of this risk and the future will bring tighter legislation to reduce the problem of noise deafness. Sensorineural hearing loss which is not accompanied by a conductive loss cannot be attributed to otosclerosis. This myth of 'cochlear otosclerosis' is not easly squelched because the concept is so eloquently extolled by well-meaning colleagues. Research on temporal bones, however, has provided incontrovertible evidence on the issue. Whenever the otosclerotic lesion is large enough to involve the inner cochlear wall and is
762
H. F. SCHUKNECHT
thus severe enough to damage the inner ear, it also fixes the stapes (Schuknecht and Kirchner, 1974). As for the effectiveness of fluorides in arresting and maturing the otosclerotic lesion, the evidence is weak at best. Certainly fluoride therapy is totally irrational in the treatment of pure sensorineural hearing loss for reasons already stated. The cause for sudden deafness is not yet known. Pathological studies on such ears in our collection show atrophy of the organ of Corti without loss of neurons, stria vascularis or other structures. The vessels appear normal and there is no hydrops or evidence of previous breaks of the membranes. The pathological picture is similar to that caused by mumps and rubella. Several controlled studies are underway in the United States to evaluate the effectiveness of steroids and vasodilators in the treatment of sudden deafness. Some of the shotgun therapies currently being advocated actually challenge the strength of the patient to survive. Some cases of sudden deafness may be due to perilymph fistula of the round or oval window, particularly when there is a precipitating incident such as head blow, blast in air, atmospheric pressure change, sneezing, straining, etc. Surgical exploration should probably be limited to those cases in which onset of the hearing loss is marked by some stressfull incident. The 'small internal auditory canal syndrome' has recently been touted as a cause of sensorineural hearing loss and/or vertigo and quite naturally decompression of the canal has been advocated as the appropriate treatment. Research on our temporal bone collection has failed to corroborate the existence of such a disorder, except, of course, in osteopetrosis and Paget's disease. Even in these cases the narrowing is insufficient to cause impingement on the contents of the canal. The existence of this syndrome is best rejected until some evidence to support it can be found in temporal bone studies. Conductive Hearing Loss
Probably no endeavor in otology is more demanding, rewarding, and at the same time frustrating, than surgery for chronic middle ear and mastoid infection. The problem of the suppurating postoperative mastoid cavity appears to have been partly eliminated by intact-canal-wall and obliteration techniques; however, recurring cholesteatoma remains a problem. The objective of performing with consistent success a one-stage operation in which the disease is eliminated and the sound transmission system is restored has eluded even the most skilled surgeons. The use of the homograft tympanic membrane and ossicular assembly appears to have little advantage over the other simpler methods and the implantation of plastic struts has been notoriously unsuccessful in one-stage procedures. Animal research has provided little information of practical value in tympanoplasty surgery. The reason for this is that the pathogenesis and course of otitis media and mastoditis are determined largely by the specific
RECENT RESEARCH AND ITS RELEVANCE TO CLINICAL OTOLOGY
763
anatomical features of the human ear. Thus, relevant animal models cannot be readily created. Research on the eustachian tube in animals and human subjects has shown the importance of tubal dysfunction as a determinant of surgical success, yet nothing much has evolved that can be translated into immediate clinical usefulness. Advances in tympanoplasty surgery will necessarily continue to be based on trial-and-error research on human subjects. It can only be hoped that these endeavours—that is, the development of new techniques in surgery—will be restricted to those otologists with large enough surgical practices and back-up facilities, such as pathology laboratories and computer facilities, to insure the validity of their observations. Certainly, there will be future improvements in chronic ear surgery; however, the consumer of the future will probably require evidence of substantial functional rewards before accepting the expense of exotic homografts or planned staging of operative procedures. Stapedectomy for otosclerosis, on the other hand, has been somewhat successful. In a recent statistical study of my own cases we determined that the mean postoperative bone-air gaps (500, 100, 2,000 Hz) for 1,000 cases were 3-39 db at 6 weeks and 10-8 at 5 years. We also learned that at 5 years post surgery the total stapedectomy methods with fat-wire or gelwire implants yielded a more efficient hearing result at 500 Hz by a factor of 5-22 db while the partial stapedectomy and piston implant yielded a more efficient result at 2,000 Hz by a factor of 2-25 db. It appears that the fluid volume displacement achieved by the small piston is not optimal for the transmission of low tones and that functional rewards can come from more closely matching the hydraulic system of the normal ear. The incidence of severe permanent sensorineural hearing loss was 1 • 2 per cent in primary stapedectomies and 3-9 per cent in revision procedures (Schuknecht and Bentkover, 1979). We should be able to improve on these results by more meticulous surgery. Again the study of temporal bones of patients who had a stapedectomy will provide information upon which to base improvements in technique (Schuknecht and Jones, 1979).
Dysequilibrium
The most common type of dysequilibrium is that caused by the degenerative changes of aging. As with presbycusis, temporal bone research has shown several types which may involve the receptor organ and/or vestibular nerve. They are manifested by momentary or constant unsteadiness, episodic vertigo or postional vertigo. Logic dictates that restraint should be exercised in the treatment of these disorders. Meniere's disease because of its prevalence is a significant health problem. In Sweden the disease has an incidence of 46:100,000 which is higher than the incidence of otosclerosis in that country (Stahle et al., 1978). An excellent model for Meniere's disease has been produced in cats and guinea pigs by simply blocking the endolymphatic duct, which in effect ablates
764
H. F. SCHUKNECHT
the function of the endolymphatic sac. This causes endolymphatic hydrops, a finding also present in ears with Meniere's disease, as well as degenerative changes in the sensory and neural structures in the apical region of the cochlea. These changes are sometimes also seen in Meniere's disease. Human ears afflicted with Meniere's disease also show ruptures of the membranous labyrinth which has not been demonstrated in animals. Furthermore, human subjects suffer episodic vertigo and fluctuating hearing loss which has not yet been demonstrated in animals. These differences may be species-related or due to insufficient survival times for the animals. The evidence favours the hypothesis that the over-accumulation of endolymph is caused by faulty resorption in the endolymphatic sac, and that the resulting distention causes ruptures of the membranes as well as interference with motion mechanics. The ruptures allow contamination of the perilymph with neurotoxic endolymph, which in turn causes a temporary paralysis of the sensorineural structures, thus accounting for the episodic vertigo and fluctuating hearing loss. In the treatment of Meniere's disease man's ingenuity knows no bounds. An enormous literature has evolved extolling every possible medical and surgical approach, and it is quite amazing that, with rare exceptions, the success rate is 70 per cent. The designing and sponsoring of new and presumably better tubes for draining the endolymphatic sac is a new pastime for some otologists. Sac procedures are done without a shred of evidence that any tube ever drained a drop of endolymph. It is entirely probable that these drain tubes become rapidly embedded in fibrous tissue but, even if they do not it seems improbable that endolymph from the cochlea could find its way into the endolymphatic duct and sac, because of intervening distorted, ruptured and collapsed membranes. There are conceptual problems with almost every form of surgical and medical treatment for Meniere's disease (Schuknecht, 1978). Possibly the idea of creating a small endolymph-perilymph fistula has some logical basis. We have tried to create such fistulas in animals but have been unsuccessful thus far because they all heal; however, this research will continue (Kimura et al., 1977). To lecture in London about positional vertigo of the benign paroxysmal type is certainly like carrying coals to Newcastle. I shall therefore engage in a subterfuge and refer to the condition as cupulolithiasis. Mr. C. S. Hallpike has had an enormous influence on my thinking on this subject. Animal experiments and human temporal bone studies show that the disorder is caused by sediment resting on the cupula of the posterior semicircular canal (Schuknecht and Ruby, 1973). Human temporal bone studies have shown such deposits in the ears of 3 patients with this type of positional vertigo. As expected, an operation has been devised to treat the condition. In this operation the posterior ampullary nerve is cut by a tympanotomy approach. Incidentally, the results have been impressive (Gacek, 1978).
RECENT RESEARCH AND ITS RELEVANCE TO CLINICAL OTOLOGY
765
Facial Nerve Lesions For as long as I can remember, the management of Bell's palsy has been a therapeutic enigma. Reports of success with medical treatments or surgical decompression are of anecdotal nature rather than statistically validated observations. The cosmetic disfiguration and mental depression that accompany facial palsy are strong motivation for aggressive therapy. Some otologic surgeons now adyocate more extensive decompression of the nerve, including the intratemporal segment. It is difficult to determine whether this recommendation is based on enthusiasm borne of surgical ability or whether the nerve is really frequently diseased in this area. I suspect that Bell's palsy is a viral neuropathy and animal experiments utilizing neuropathic viruses should be done to attempt specifically to create a model for Bell's palsy. The value of surgical decompression of the facial nerve in herpes zoster oticus is even more questionable. The one and only example of herpes zoster oticus in our temporal bone collection shows severe degeneration of the facial, cochlear and vestibular nerves in the internal auditory canal and it is difficult to see how decompression could have aided this case. Facial nerve palsies which occur at the time of temporal bone fractures are more logical candidates for surgery. When the fracture is of the transverse type there is good reason to explore the intratemporal segment because the fracture frequently extends through this area. When the palsy is delayed the value of surgery is less definite and my personal policy is not to explore. The mandate for the otologist of the future is quite clear—perform controlled studies to clarify the confusion surrounding facial nerve lesions. Neoplasia One of the success stories of modern otology is the refinement of surgical methods for the removal of schwannoma of the vestibular nerve; credit for this achievement goes almost singularly to William House. In our temporal bone collection the incidence of occult schwannomata is 0- 87 per cent or 870:100,000. The incidence of surgically treated vestibular schwannomata, on the other hand, is about 15:100,000: therefore it would appear that only one of every 580 or 0-17 per cent of these neoplasms ever becomes clinically manifest. More consistent early detection and improved surgical techniques can be expected in this type of surgery. Improved resolution in CT scanners will eventually totally replace contrast dye studies in the diagnoses of these tumors. Preoperative vascular embolisation as an aid in controlling bleeding during the removal of glomus body tumors is helpful in dealing with these difficult lesions. The procedure however carries some risk of accidental embolisation of the internal carotid system and therefore may not come into widespread use. Recent reports by House and Hitselberger (1976) and
766
H. F. SCHUKNECHT
by Fisch and Pillsbury (1979) on infratemporal approaches to the skull base show what can be done with exceptional anatomical knowledge and technical skill. It appears that for some time to come, excisional surgery will remain the principal approach to the control of neoplastic disease. Computer Science
Otology like all of medicine is benefiting enormously from the application of computers to clinical endeavours, research, and administrative functions. The marvels of the science will continue to impress and baffle most of us. The most recent triumphs in clinical otology, of course, are the applications of signal averaging techniques to the analysis of eye movement in the form of electronystagmography and to cochlear and brain-stem responses in the form of evoked response audiometry. These powerful new diagnostic devices are rapidly becoming the ordinary tools of our trade. Signal averaging is absolutely essential to research on the physiological behavior of the auditory and vestibular systems, and data processing is a necessary aid for most clinical and laboratory research.
1.
2. 3.
4.
5. 6.
Predictions The paucity of healthy cochlear nerve fibres in most profoundly deaf ears will provoke otologists to settle for a cochlear implant which conveys only crude sounds. Meanwhile, research will continue on methods for introducing more complex signals at higher levels in the auditory system. Presbycusis will become more prevalent in our aging population and the hearing aid industry will thrive. Rubella, mumps and measles deafness will disappear with the wide spread use of highly effective vaccines, and the prevalence of otitic infections will continue to decline as new synthetic antibiotic drugs become available. The consumers of health care will eventually require evidence of effectiveness before medical or surgical treatments will qualify for compensation. This will end the era of fluoride therapy for otosclerosis, vasodilators for presbycusis, shotgun therapy for sudden deafness, decompression of the so-called narrow internal auditory canal for sensorineural hearing loss, staged tympanoplasties, shunt procedures for Meniere's disease and facial nerve decompressions for Bell's palsy. The management of neoplasms of the ear will remain principally an extirpative process, although computer assisted radiotherapy and chemotherapy will serve as important therapeutic aids. New and highly refined behavioral and electrophysiological evoked response tests will permit more precise site of lesion determinations
RECENT RESEARCH AND ITS RELEVANCE TO CLINICAL OTOLOGY
767
in the auditory and vestibular system, which will lead to improved capability for diagnosis of otological and CNS disease. 7. The otologist of the future will want to have more training in the neurosciences in order to communicate and work more effectively with colleagues in the neighbouring fields of audiology, neurology and neurosurgery. Thank you, ladies and gentlemen, for the opportunity of paying tribute to James Yearsley and for the privilege of sharing with you some of my observations and interpretations of happenings—past, present, and future —in the discipline of otology. BIBLIOGRAPHY FISCH, U., and PILLSBURY, H. (1979) Archives of Otolaryngology, 105, 99. GACEK, R. (1978) Annals of Otology, Rhinology and Laryngology, 87, 300. HOUSE, W., and HITSELBERGER, W. (1976) Archives of Otolaryngology, 102, 334. KIMURA, R., SCHUKNECHT, H., OTA, C , and JONES, D. (1977) Archives of Otolaryngologv, 217,
123.
•
OTTE, J., SCHUKNECHT, H., and KERR, A. (1978) The Laryngoscope, 88, 1231. SCHUKNECHT, H., and RUBY, R. (1973) Adv. Oto-Rhino-Laryng., 20, 434. SCHUKNECHT, H., and KIRCHNER, J. (1974) The Laryngoscope, 84, 766.
SCHUKNECHT, H. (1978) Journal of Continuing Education in O.R.L. & Allergy, 40, 15. SCHUKNECHT, H., and JONES, D. (1979) The Annals of Otology, Rhinology and Laryngology, Vol. 5,88, 1. SCHUKNECHT, H., and BENTKOVER, S. (1979) Controversy in Otolaryngology, ed. James Snow. Philadelphia, PA. W. B. Saunders Co., in press. SCOTT STEVENSON, R., and GUTHRIE, D. (1949) A History of Oto-Laryngology, Edinburgh,
E. and S. Livingstone. STAHLE, S., ARENBERG, K. , and STAHLE, J. (1978) Archives of Otolaryngology, 104, 99.
GENERAL REFERENCES BULL, T., RANSOME, J., and HOLDEN, H. (1978) Recent Advances in Otolaryngology No. 5
Edinburgh, Churchill Livingstone. FRASER, G. (1976) The Causes of Profound Deafness in Childhood. Baltimore, Maryland, John Hopkins University Press. KONIGSMARK, B., and GORLIN, R. (1976) Genetic and Metabolic Deafness. Philadelphia, Pennsylvania, W. B. Saunders Company. RASMUSSEN, G., and WINDLE, W. (1960) Neural Mechanisms of the Auditory and Vestibular Systems. Springfield, Illinois, Charles C. Thomas. SCHUKNECHT, H. (1974) Pathology of the Ear, Cambridge, Massachusetts, Harvard University Press. SILVERSTEIN, H., and NORRELL, H. (1977) Neurological Surgery of the Ear. Birmingham, Alabama, Aesculapius Publishing Company. TOWER, D. (1975) The Nervous System Vol. 3, Human Communication and its Disorders. New York, Vol. ed. Eagles, E., Raven Press. WECHSLER, H., GURIN, J., and CAHILL, G. (1977) The Horizons of Health. Cambridge,
Massachusetts, Harvard University Press.
Recent research and its relevance to clinical otology* By HAROLD F. SCHUKNECHT,
M.D.f
IT is an exceptional pleasure to be once again with my British friends and colleagues, and I feel honored to have been chosen to present this address. The man whom we are honoring tonight, James Yearsley (Fig. 1), was one of the pioneers of British otolaryngology, and I am pleased that my name can be linked with his in this small way. Yearsley was born in 1805, studied at St. Bartholomew's Hospital and received his medical degree at St. Andrew's. In 1838 he founded the Metropolitan Ear Institution which later became and remains your well-known Metropolitan Ear, Nose and Throat Hospital. He was one of the founders of the Medical Directory which preceded your Medical Registry. Probably his most significant contribution to otology was his demonstration that prostheses, such as pledgets of moist cotton-wool, could be used to enhance sound transmission in defective middle ears. He carried on a large practice in London and died in 1869 at the age of 64 (Scott Stevenson and Guthrie, 1949). Your committee suggested the title 'Recent Research And Its Relevance To Clinical Otology'. It was with some reluctance that I accepted a subject of such broad scope. In dealing with such a subject there is a strong inclination to give an account of facts which are probably well-known to everyone and to make a large number of predictions with the expectation that a few of them will come true. I have made a concerted effort to avoid this approach, with, I fear, only partial success. I may also have transgressed the rule that a speaker should limit his remarks to subjects about which he has some knowledge, but you can be the judge of that. Sensorineural Hearing Loss Recently there has been a great deal of noisy enthusiasm for the cochlear implant; but what is the real potential of this device for the rehabilitation of profoundly deaf individuals? Single electrode implants are a reality, of course, and the ingenuity and courage of surgeons who have implanted them deserves our admiration. However, the implant is receiving too much attention at this time. In the first place, the total pool of candidates suitable for implantation is quite small. Secondly, the technology is * Twenty-Fifth James Yearsley lecture presented at the Royal College of Medicine on March 2, 1979. f Chief, Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Professor of Otology and Laryngology, Harvard Medical School. 759
760
H. F. SCHUKNECHT
FIG.
1
FIG.
2
RECENT RESEARCH AND ITS RELEVANCE TO CLINICAL OTOLOGY
761
too primitive to justify widespread use at this time. Probably the most serious obstacles in the path of success of implantation are the paucity of cochlear nerve fibres in most ears with profound deafness, and the additional damage which is almost certain to result from implantation (Otte et ah, 1978). None the less, the drama will proceed and some good may eventually come of it. A much greater health problem facing us is the great multitude of disabled people with subtotal sensorineural hearing loss. With the virtual elimination of acute bacterial infection as a cause for hearing loss, the most common type now encountered is presbycusis. Several pathological types of presbycusis have now been described and the success of amplification depends entirely on the type. For example, in the strial atrophy type in which hair cells and neurons are functional, stimulus coding and consequently speech discrimination are excellent and amplification is highly successful. In the neural atrophy type, on the other hand, in spite of functional stria and hair cells, the discrimination is poor and amplification is less helpful (Schuknecht, 1974). Presbycusis is caused by degenerative changes occurring in 'fixed postmitotic' cells. These specialized cells have no regenerative powers and once damaged cannot be replaced. Presbycusis should be viewed as the auditory manifestation of a diffuse process which involves all the body tissues. Within the fourth decade of life there already is decreased efficiency in some organs and of the individual as a whole. In the fifth decade there is a more apparent reduction in efficiency, and the further passage of time brings a cascading of senile events which terminate in death in the seventh or eighth decade of life. The manner in which we age is largely determined by genetic factors. Unless an unexpected breakthrough occurs in the research on aging there will be no prevention of presbycusis and it will become increasingly prevalent as survival time increases. The effect on hearing of a lifetime of noise exposure is not known. How harmful are household noises and street noises? This question has not been answered. Certainly the noises of industry, motor vehicles, firearms and amplified music are responsible for many handicapping losses. Many animal studies have been performed in which various acoustic stimuli have been correlated with morphological changes in the cochlea. These studies have aided in establishing damage risk criteria. There is now general awareness of this risk and the future will bring tighter legislation to reduce the problem of noise deafness. Sensorineural hearing loss which is not accompanied by a conductive loss cannot be attributed to otosclerosis. This myth of 'cochlear otosclerosis' is not easly squelched because the concept is so eloquently extolled by well-meaning colleagues. Research on temporal bones, however, has provided incontrovertible evidence on the issue. Whenever the otosclerotic lesion is large enough to involve the inner cochlear wall and is
762
H. F. SCHUKNECHT
thus severe enough to damage the inner ear, it also fixes the stapes (Schuknecht and Kirchner, 1974). As for the effectiveness of fluorides in arresting and maturing the otosclerotic lesion, the evidence is weak at best. Certainly fluoride therapy is totally irrational in the treatment of pure sensorineural hearing loss for reasons already stated. The cause for sudden deafness is not yet known. Pathological studies on such ears in our collection show atrophy of the organ of Corti without loss of neurons, stria vascularis or other structures. The vessels appear normal and there is no hydrops or evidence of previous breaks of the membranes. The pathological picture is similar to that caused by mumps and rubella. Several controlled studies are underway in the United States to evaluate the effectiveness of steroids and vasodilators in the treatment of sudden deafness. Some of the shotgun therapies currently being advocated actually challenge the strength of the patient to survive. Some cases of sudden deafness may be due to perilymph fistula of the round or oval window, particularly when there is a precipitating incident such as head blow, blast in air, atmospheric pressure change, sneezing, straining, etc. Surgical exploration should probably be limited to those cases in which onset of the hearing loss is marked by some stressfull incident. The 'small internal auditory canal syndrome' has recently been touted as a cause of sensorineural hearing loss and/or vertigo and quite naturally decompression of the canal has been advocated as the appropriate treatment. Research on our temporal bone collection has failed to corroborate the existence of such a disorder, except, of course, in osteopetrosis and Paget's disease. Even in these cases the narrowing is insufficient to cause impingement on the contents of the canal. The existence of this syndrome is best rejected until some evidence to support it can be found in temporal bone studies. Conductive Hearing Loss
Probably no endeavor in otology is more demanding, rewarding, and at the same time frustrating, than surgery for chronic middle ear and mastoid infection. The problem of the suppurating postoperative mastoid cavity appears to have been partly eliminated by intact-canal-wall and obliteration techniques; however, recurring cholesteatoma remains a problem. The objective of performing with consistent success a one-stage operation in which the disease is eliminated and the sound transmission system is restored has eluded even the most skilled surgeons. The use of the homograft tympanic membrane and ossicular assembly appears to have little advantage over the other simpler methods and the implantation of plastic struts has been notoriously unsuccessful in one-stage procedures. Animal research has provided little information of practical value in tympanoplasty surgery. The reason for this is that the pathogenesis and course of otitis media and mastoditis are determined largely by the specific
RECENT RESEARCH AND ITS RELEVANCE TO CLINICAL OTOLOGY
763
anatomical features of the human ear. Thus, relevant animal models cannot be readily created. Research on the eustachian tube in animals and human subjects has shown the importance of tubal dysfunction as a determinant of surgical success, yet nothing much has evolved that can be translated into immediate clinical usefulness. Advances in tympanoplasty surgery will necessarily continue to be based on trial-and-error research on human subjects. It can only be hoped that these endeavours—that is, the development of new techniques in surgery—will be restricted to those otologists with large enough surgical practices and back-up facilities, such as pathology laboratories and computer facilities, to insure the validity of their observations. Certainly, there will be future improvements in chronic ear surgery; however, the consumer of the future will probably require evidence of substantial functional rewards before accepting the expense of exotic homografts or planned staging of operative procedures. Stapedectomy for otosclerosis, on the other hand, has been somewhat successful. In a recent statistical study of my own cases we determined that the mean postoperative bone-air gaps (500, 100, 2,000 Hz) for 1,000 cases were 3-39 db at 6 weeks and 10-8 at 5 years. We also learned that at 5 years post surgery the total stapedectomy methods with fat-wire or gelwire implants yielded a more efficient hearing result at 500 Hz by a factor of 5-22 db while the partial stapedectomy and piston implant yielded a more efficient result at 2,000 Hz by a factor of 2-25 db. It appears that the fluid volume displacement achieved by the small piston is not optimal for the transmission of low tones and that functional rewards can come from more closely matching the hydraulic system of the normal ear. The incidence of severe permanent sensorineural hearing loss was 1 • 2 per cent in primary stapedectomies and 3-9 per cent in revision procedures (Schuknecht and Bentkover, 1979). We should be able to improve on these results by more meticulous surgery. Again the study of temporal bones of patients who had a stapedectomy will provide information upon which to base improvements in technique (Schuknecht and Jones, 1979).
Dysequilibrium
The most common type of dysequilibrium is that caused by the degenerative changes of aging. As with presbycusis, temporal bone research has shown several types which may involve the receptor organ and/or vestibular nerve. They are manifested by momentary or constant unsteadiness, episodic vertigo or postional vertigo. Logic dictates that restraint should be exercised in the treatment of these disorders. Meniere's disease because of its prevalence is a significant health problem. In Sweden the disease has an incidence of 46:100,000 which is higher than the incidence of otosclerosis in that country (Stahle et al., 1978). An excellent model for Meniere's disease has been produced in cats and guinea pigs by simply blocking the endolymphatic duct, which in effect ablates
764
H. F. SCHUKNECHT
the function of the endolymphatic sac. This causes endolymphatic hydrops, a finding also present in ears with Meniere's disease, as well as degenerative changes in the sensory and neural structures in the apical region of the cochlea. These changes are sometimes also seen in Meniere's disease. Human ears afflicted with Meniere's disease also show ruptures of the membranous labyrinth which has not been demonstrated in animals. Furthermore, human subjects suffer episodic vertigo and fluctuating hearing loss which has not yet been demonstrated in animals. These differences may be species-related or due to insufficient survival times for the animals. The evidence favours the hypothesis that the over-accumulation of endolymph is caused by faulty resorption in the endolymphatic sac, and that the resulting distention causes ruptures of the membranes as well as interference with motion mechanics. The ruptures allow contamination of the perilymph with neurotoxic endolymph, which in turn causes a temporary paralysis of the sensorineural structures, thus accounting for the episodic vertigo and fluctuating hearing loss. In the treatment of Meniere's disease man's ingenuity knows no bounds. An enormous literature has evolved extolling every possible medical and surgical approach, and it is quite amazing that, with rare exceptions, the success rate is 70 per cent. The designing and sponsoring of new and presumably better tubes for draining the endolymphatic sac is a new pastime for some otologists. Sac procedures are done without a shred of evidence that any tube ever drained a drop of endolymph. It is entirely probable that these drain tubes become rapidly embedded in fibrous tissue but, even if they do not it seems improbable that endolymph from the cochlea could find its way into the endolymphatic duct and sac, because of intervening distorted, ruptured and collapsed membranes. There are conceptual problems with almost every form of surgical and medical treatment for Meniere's disease (Schuknecht, 1978). Possibly the idea of creating a small endolymph-perilymph fistula has some logical basis. We have tried to create such fistulas in animals but have been unsuccessful thus far because they all heal; however, this research will continue (Kimura et al., 1977). To lecture in London about positional vertigo of the benign paroxysmal type is certainly like carrying coals to Newcastle. I shall therefore engage in a subterfuge and refer to the condition as cupulolithiasis. Mr. C. S. Hallpike has had an enormous influence on my thinking on this subject. Animal experiments and human temporal bone studies show that the disorder is caused by sediment resting on the cupula of the posterior semicircular canal (Schuknecht and Ruby, 1973). Human temporal bone studies have shown such deposits in the ears of 3 patients with this type of positional vertigo. As expected, an operation has been devised to treat the condition. In this operation the posterior ampullary nerve is cut by a tympanotomy approach. Incidentally, the results have been impressive (Gacek, 1978).
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Facial Nerve Lesions For as long as I can remember, the management of Bell's palsy has been a therapeutic enigma. Reports of success with medical treatments or surgical decompression are of anecdotal nature rather than statistically validated observations. The cosmetic disfiguration and mental depression that accompany facial palsy are strong motivation for aggressive therapy. Some otologic surgeons now adyocate more extensive decompression of the nerve, including the intratemporal segment. It is difficult to determine whether this recommendation is based on enthusiasm borne of surgical ability or whether the nerve is really frequently diseased in this area. I suspect that Bell's palsy is a viral neuropathy and animal experiments utilizing neuropathic viruses should be done to attempt specifically to create a model for Bell's palsy. The value of surgical decompression of the facial nerve in herpes zoster oticus is even more questionable. The one and only example of herpes zoster oticus in our temporal bone collection shows severe degeneration of the facial, cochlear and vestibular nerves in the internal auditory canal and it is difficult to see how decompression could have aided this case. Facial nerve palsies which occur at the time of temporal bone fractures are more logical candidates for surgery. When the fracture is of the transverse type there is good reason to explore the intratemporal segment because the fracture frequently extends through this area. When the palsy is delayed the value of surgery is less definite and my personal policy is not to explore. The mandate for the otologist of the future is quite clear—perform controlled studies to clarify the confusion surrounding facial nerve lesions. Neoplasia One of the success stories of modern otology is the refinement of surgical methods for the removal of schwannoma of the vestibular nerve; credit for this achievement goes almost singularly to William House. In our temporal bone collection the incidence of occult schwannomata is 0- 87 per cent or 870:100,000. The incidence of surgically treated vestibular schwannomata, on the other hand, is about 15:100,000: therefore it would appear that only one of every 580 or 0-17 per cent of these neoplasms ever becomes clinically manifest. More consistent early detection and improved surgical techniques can be expected in this type of surgery. Improved resolution in CT scanners will eventually totally replace contrast dye studies in the diagnoses of these tumors. Preoperative vascular embolisation as an aid in controlling bleeding during the removal of glomus body tumors is helpful in dealing with these difficult lesions. The procedure however carries some risk of accidental embolisation of the internal carotid system and therefore may not come into widespread use. Recent reports by House and Hitselberger (1976) and
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by Fisch and Pillsbury (1979) on infratemporal approaches to the skull base show what can be done with exceptional anatomical knowledge and technical skill. It appears that for some time to come, excisional surgery will remain the principal approach to the control of neoplastic disease. Computer Science
Otology like all of medicine is benefiting enormously from the application of computers to clinical endeavours, research, and administrative functions. The marvels of the science will continue to impress and baffle most of us. The most recent triumphs in clinical otology, of course, are the applications of signal averaging techniques to the analysis of eye movement in the form of electronystagmography and to cochlear and brain-stem responses in the form of evoked response audiometry. These powerful new diagnostic devices are rapidly becoming the ordinary tools of our trade. Signal averaging is absolutely essential to research on the physiological behavior of the auditory and vestibular systems, and data processing is a necessary aid for most clinical and laboratory research.
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Predictions The paucity of healthy cochlear nerve fibres in most profoundly deaf ears will provoke otologists to settle for a cochlear implant which conveys only crude sounds. Meanwhile, research will continue on methods for introducing more complex signals at higher levels in the auditory system. Presbycusis will become more prevalent in our aging population and the hearing aid industry will thrive. Rubella, mumps and measles deafness will disappear with the wide spread use of highly effective vaccines, and the prevalence of otitic infections will continue to decline as new synthetic antibiotic drugs become available. The consumers of health care will eventually require evidence of effectiveness before medical or surgical treatments will qualify for compensation. This will end the era of fluoride therapy for otosclerosis, vasodilators for presbycusis, shotgun therapy for sudden deafness, decompression of the so-called narrow internal auditory canal for sensorineural hearing loss, staged tympanoplasties, shunt procedures for Meniere's disease and facial nerve decompressions for Bell's palsy. The management of neoplasms of the ear will remain principally an extirpative process, although computer assisted radiotherapy and chemotherapy will serve as important therapeutic aids. New and highly refined behavioral and electrophysiological evoked response tests will permit more precise site of lesion determinations
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in the auditory and vestibular system, which will lead to improved capability for diagnosis of otological and CNS disease. 7. The otologist of the future will want to have more training in the neurosciences in order to communicate and work more effectively with colleagues in the neighbouring fields of audiology, neurology and neurosurgery. Thank you, ladies and gentlemen, for the opportunity of paying tribute to James Yearsley and for the privilege of sharing with you some of my observations and interpretations of happenings—past, present, and future —in the discipline of otology. BIBLIOGRAPHY FISCH, U., and PILLSBURY, H. (1979) Archives of Otolaryngology, 105, 99. GACEK, R. (1978) Annals of Otology, Rhinology and Laryngology, 87, 300. HOUSE, W., and HITSELBERGER, W. (1976) Archives of Otolaryngology, 102, 334. KIMURA, R., SCHUKNECHT, H., OTA, C , and JONES, D. (1977) Archives of Otolaryngologv, 217,
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OTTE, J., SCHUKNECHT, H., and KERR, A. (1978) The Laryngoscope, 88, 1231. SCHUKNECHT, H., and RUBY, R. (1973) Adv. Oto-Rhino-Laryng., 20, 434. SCHUKNECHT, H., and KIRCHNER, J. (1974) The Laryngoscope, 84, 766.
SCHUKNECHT, H. (1978) Journal of Continuing Education in O.R.L. & Allergy, 40, 15. SCHUKNECHT, H., and JONES, D. (1979) The Annals of Otology, Rhinology and Laryngology, Vol. 5,88, 1. SCHUKNECHT, H., and BENTKOVER, S. (1979) Controversy in Otolaryngology, ed. James Snow. Philadelphia, PA. W. B. Saunders Co., in press. SCOTT STEVENSON, R., and GUTHRIE, D. (1949) A History of Oto-Laryngology, Edinburgh,
E. and S. Livingstone. STAHLE, S., ARENBERG, K. , and STAHLE, J. (1978) Archives of Otolaryngology, 104, 99.
GENERAL REFERENCES BULL, T., RANSOME, J., and HOLDEN, H. (1978) Recent Advances in Otolaryngology No. 5
Edinburgh, Churchill Livingstone. FRASER, G. (1976) The Causes of Profound Deafness in Childhood. Baltimore, Maryland, John Hopkins University Press. KONIGSMARK, B., and GORLIN, R. (1976) Genetic and Metabolic Deafness. Philadelphia, Pennsylvania, W. B. Saunders Company. RASMUSSEN, G., and WINDLE, W. (1960) Neural Mechanisms of the Auditory and Vestibular Systems. Springfield, Illinois, Charles C. Thomas. SCHUKNECHT, H. (1974) Pathology of the Ear, Cambridge, Massachusetts, Harvard University Press. SILVERSTEIN, H., and NORRELL, H. (1977) Neurological Surgery of the Ear. Birmingham, Alabama, Aesculapius Publishing Company. TOWER, D. (1975) The Nervous System Vol. 3, Human Communication and its Disorders. New York, Vol. ed. Eagles, E., Raven Press. WECHSLER, H., GURIN, J., and CAHILL, G. (1977) The Horizons of Health. Cambridge,
Massachusetts, Harvard University Press.
